1. Field of the Invention
This invention relates to an electrophotographic photoreceptor, and more specifically to a novel electrophotographic photoreceptor provided with a photosensitive layer which contains a specific azo compound.
2. Description of the Related Art
In recent years, the utility of electrophotography is not limited to the field of copying machines but has expanded to various other fields where photographic techniques have conventionally been used, such as printing plates, slide films and microfilms. Investigations are also under way in order to apply electrophotography to high-speed printers which make use of a laser or LED as a light source. The demand is hence moving toward a wide variety of electrophotographic photoreceptors of higher quality.
As photoreceptors for electrophotography, those having a photosensitive layer composed of an inorganic photoconductive material such as amorphous selenium, cadmium sulfide or zinc oxide as a principal component have been used primarily to date. Although photoreceptors formed of these inorganic materials are useful, they are still accompanied by various drawbacks.
With a view toward making improvements to the above drawbacks, electrophotographic photoreceptors making use various organic materials as photoconductive materials have been proposed and have started finding practical utility in recent years. Needless to say, an electrophotographic photoreceptor must have both carrier producing function and carrier transporting function. As organic compounds usable as carrier producing materials, numerous pigments have been proposed such as phthalocyanine type pigments, polycyclic quinoline type pigments, indigo type pigments, dioxazine type pigments, quinacridone type pigments and azo type pigments. There are however very few pigments which have been put to practical use. Since a carrier transporting substance can be chosen only from a limited range, it has not been obtained under the circumstances any carrier transporting substance which can meet satisfactorily the diversified demands for the electrophotographic process.